Diastereoselective Synthesis of 2‑Arylmethylene-6-hydroxyspiro[4.5]deca-7-ones via FeCl3·6H2O‑Catalyzed Spiroannulation/Hydride Transfer of 6‑(5-Arylpent-4-yn-1-yl)-7-oxabicyclo[4.1.0]heptan-2-ols

In the presence of a catalytic amount of FeCl3·6H2O, 6-(5-arylpent-4-yn-1-yl)-7-oxabicyclo­[4.1.0]­heptan-2-ols underwent attack of the pendant acetylene at the iron-activated oxirane to give a vinylic carbocation. Hydride transfer from the carbinol carbon to the newly formed cation center furnished 2-arylmethylene-6-hydroxy­spiro­[4.5]­deca-7-ones in excellent stereoselectivity and good yields.